There are many methods of performing the functions of a gyroscope: rotating disc, rotating sphere, quartz tuning fork, fiber optic laser, hemispherical resonance, etc. In addition there are a number of known micromechanical gyroscope implementations, such as gimballed gyroscopes, and polysilicon and metal tuning fork gyroscopes.
The "bulk" or non-micromechanical gyroscopes are much larger, heavier, and expensive. Previous micromechanical gyroscopes have low sensitivity, are difficult to fabricate due to multiple masking and processing steps, and have problems with movable masses coming into contact with electrode material and sticking.
Sticking occurs when a resonating mass comes into contact with an underlying metal electrode, typically gold, and fails to spring free, ultimately ending in device failure. The magnitude of drive forces and pressures that can be applied to a gyroscope prone to sticking is necessarily limited by this phenomenon.